It allows to interact with BAP from within emacs. For example, bap-open-file (C-c C-b o) opens a file with BAP and emits the IR to an Emacs buffer. bap-mode hightlights the syntax and allows to quickly navigate the code (e.g. C-c C-b m to jump to the main function). https://github.com/fkie-cad/bap-mode